Flash memory devices are non-volatile memory media in which stored data is not lost even when power is turned off. Flash memory devices can be advantageous in having a high processing speed when operations are performed such as recording, reading, and deleting, etc. Therefore, flash memory devices have been widely used in data storage for Bios for personal computers (PC), a set-top box, a printer, and a network server, etc. Recently, flash memory devices have widespread application in devices such as digital cameras and cellular phones.
However, as flash memory devices have become more highly integrated, the size of a unit cell of the flash memory is reduced, and in turn, the spatial interval between gate areas forming the unit cell are also reduced so that voids are generated when forming a metal wire.